Geir Sagvolden - Academia.edu (original) (raw)

Papers by Geir Sagvolden

Structural health monitoring (SHM) systems are recognized as a key element in a modern and effici... more Structural health monitoring (SHM) systems are recognized as a key element in a modern and efficient approach to structural lifecycle management. With novel applications of advanced materials, such as extensive use of fibre reinforced composites on aircraft, further advances in monitoring and inspection techniques are required. This is especially relevant for repairs on primary (i.e. load bearing) military aircraft composite structures, where traditional non-destructive inspection methods alone may be insufficient for certification of the repair. Optical fibre sensor systems with continuous in-flight monitoring are considered a promising approach to providing the necessary information on the status of the repaired area. Fibre optic sensor systems commonly involve the use fibre Bragg grating (FBG) sensors bonded to or embedded in the structure. As an element in a certified repair strategy, the limitations of the load transfer from the structure to the sensor must be known. Hence, extensive analysis and testing must be done before introducing any adhesive system/optical fibre combination as part of the SHM system. This paper presents experimental test results obtained for the interface properties of optical fibres with polyimide or Ormocer® coating embedded in an adhesive. Three different adhesives, which are all relevant for military aircraft primary composite structural repairs, are included in the test program. A modified fibre pull-out test setup is applied for estimating the interfacial shear strength (IFSS) for each of the six combinations of adhesive and optical fibre, at two different nominal embedded lengths of 0.5 mm and 1.0 mm. For the polyimide coated fibre, the IFSS values obtained for the three adhesives from fibre pull-out do not differ significantly. The highest IFSS values are obtained at a nominal embedded length of 0.5 mm. The optical fibre with Ormocer® coating seems to have the strongest bond to the adhesives, but results in core pull-out instead of fibre pull-out. The obtained IFSS values for the core/coating interface of the Ormocer® coated fibre are not directly comparable with the IFSS values obtained for the polyimide coated fibre, but they still demonstrate the load transfer properties and the potential of the optical fibre for obtaining accurate strain measurements. As an overall conclusion, the polyimide coated fibre is considered the most appropriate for use in a fibre optic sensor system for SHM.

Proceedings of the International Conference on Port and Ocean Engineering Under Arctic Conditions, 2011

Fiber optic structural monitoring systems are an increasingly popular tool for overload warning, ... more Fiber optic structural monitoring systems are an increasingly popular tool for overload warning, fatigue life management and decision support on ship hull operation. These systems have also found a range of applications outside hull monitoring due to the excellent performance of fiber optic sensor and communication systems in harsh environments. When low noise strain measurements are coupled with structural response models, parameters such as forces, moments, displacements, and structural utilization may be measured on almost any detail of interest. Furthermore, forecasts of extremal observations based on continuous measurements of these parameters are being used to ensure operation within acceptable limits. The authors give an introduction to the measurement and processing techniques and what they offer, and use examples from an Ice Response Monitoring system installed on a Norwegian icebreaker.

Proceedings of SPIE, Jun 12, 2000

ABSTRACT We report on the instrumentation of a high-speed air-cushion catamaran (Surface Effect S... more ABSTRACT We report on the instrumentation of a high-speed air-cushion catamaran (Surface Effect Ship) with more than 50 fibre optic Bragg grating strain gauges, as well as conventional resistive strain gauges, accelerometers, a Motion Reference Unit and Global ...

Proceedings of the National Academy of Sciences of the United States of America, Jan 19, 1999

The adhesion forces of cervical carcinoma cells in tissue culture were measured by using the mani... more The adhesion forces of cervical carcinoma cells in tissue culture were measured by using the manipulation force microscope, a novel atomic force microscope. The forces were studied as a function of time and temperature for cells cultured on hydrophilic and hydrophobic polystyrene substrates with preadsorbed proteins. The cells attached faster and stronger at 37°C than at 23°C and better on hydrophilic than on hydrophobic substrates, even though proteins adsorb much better to the hydrophobic substrates. Because cell adhesion serves to control several stages in the cell cycle, we anticipate that the manipulation force microscope can help clarify some cell-adhesion related issues.

SPIE eBooks, 2000

A fiber Bragg grating sensor system consisting of 56 sensors has been developed to monitor the st... more A fiber Bragg grating sensor system consisting of 56 sensors has been developed to monitor the structural dynamical response of an in-operation composite hull naval vessel. The distributed array of wavelength-division multiplexed Bragg grating strain sensors has been utilized to measure: global hull bending with Bragg grating sensor pairs; local strain concentrations with Bragg grating rosettes; vibrational response of the ship's waterjet propulsion system; and large dynamic strain response in the wet deck region from wave slamming in rough seas. In addition to monitoring the ship's normal vibrations and bending moments, monitoring the response of the ship to wave slamming (i.e. wave impacts) - especially in the wet deck region of the catamaran - is of some importance because it can lead to large scale damage in the ship.

Measurement Science and Technology, Apr 1, 2002

... Sandwich materials may for instance require more sensors than a steel structure due to the po... more ... Sandwich materials may for instance require more sensors than a steel structure due to the potentially ... and consequently the grid of sensors must be fairly dense on a complex sandwich structure such as ... there is a desire to characterize the strain condition in the hull all the way ...

Behavioural Brain Research, Mar 1, 2009

Several existing theoretical models of Attention Deficit Hyperactivity Disorder (ADHD) predict th... more Several existing theoretical models of Attention Deficit Hyperactivity Disorder (ADHD) predict that a high or low learning rate contributes to some cases of ADHD; and that this is controlled by the dopamine signal. The Spontaneously Hypertensive (Hyperactive) Rat has an abnormal Dopamine Transporter (DAT), which is likely to be hypofunctional, thereby increasing the dopamine concentration and the learning rate. We therefore test the prediction that the SHR learns too fast. Using a variable interval reinforcement schedule, we looked for increased responding within each interval, at around the durations of the last three intervals. At the time predicted by the previous interval, SHR responded significantly (10%) more than their baseline rate, and control WKY rats similarly less than their baseline. At the time predicted by the second (and third) previous intervals, there were minor trends (and no change) in the same direction. In summary, at the times predicted, SHR respond more than control rats. The effect size is insufficient to account for all the differences from control rats, such as their nearly threefold greater operant responding. At the times when SHR increase responding, WKY suppress it. This demonstrates similar learning to the SHR but the opposite response, probably due to anxiety about the bang accompanying reinforcer delivery: WKY are known to have a very negative response to stress. Interval schedules with randomised interval lengths have considerable potential for assessing multiple causes of behaviour, particularly those acting over short timecourses. Alterations in learning rate are not a sufficient explanation for either SHR or ADHD difference from controls.

Behavioral and Neural Biology, Sep 1, 1992

Childhood hyperactivity (attention-deficit hyperactivity disorder, ADHD) is a behavior disorder a... more Childhood hyperactivity (attention-deficit hyperactivity disorder, ADHD) is a behavior disorder affecting 2-6% of grade-school children. The main symptoms are attention problems and hyperkinesis. The disorder is commonly treated with psychomotor stimulants, usually methylphenidate hydrochloride (ritalin) or d-amphetamine. Neither the cause of the disorder nor the basis of the effectiveness of the drug treatment is well understood. Differences in reinforcement processes have been implicated as part of the underlying problem. The main purpose of the present research was to investigate reinforcement processes and motor characteristics with and without stimulant medication in SHR, as an animal model of ADHD, and WKY controls, its normoactive progenitor strain. SHR behavior turned out to be more sensitive to immediate reinforcement and proportionately less sensitive to delayed reinforcement when compared to the behavior of WKY, as demonstrated by systematic changes in rates of responding throughout fixed-interval schedules of reinforcement of bar-presses by water. The psychomotor stimulants weakened the control by immediate reinforcers and strengthened the control by delayed reinforcers, with the effect of the drugs being more pronounced in WKY than in SHR. The results are consistent with clinical observations that ADHD children are less willing than others to accept "delayed gratification" and that methylphenidate increases the control of delayed reward over their behavior.

Review of Scientific Instruments, Jun 1, 1999

The manipulation force microscope is a novel atomic force microscope adapted to measuring the for... more The manipulation force microscope is a novel atomic force microscope adapted to measuring the force necessary to displace micron-size samples adhering to surfaces. It has successfully characterized the adhesion of both proteins and living cells to substrates. This instrument enables measurement of samples not previously accessible to atomic force microscopes. Here, we give a detailed account of this new method, and report on computer simulations and models to assist the interpretation of data.

ABSTRACT The authors describe a system which will, at about 10 installations in continuous operat... more ABSTRACT The authors describe a system which will, at about 10 installations in continuous operation after 2002, be the first fiber optic sensor system for ship hull monitoring with a wide user base. The experiences made with these systems in the coming years will provide valuable information on the design, reliability and possible use of such systems, and provide a basis for further development.

Behavioural Brain Research, Mar 1, 2009

Several existing theoretical models of Attention Deficit Hyperactivity Disorder (ADHD) predict th... more Several existing theoretical models of Attention Deficit Hyperactivity Disorder (ADHD) predict that a high or low learning rate contributes to some cases of ADHD; and that this is controlled by the dopamine signal. The Spontaneously Hypertensive (Hyperactive) Rat has an abnormal Dopamine Transporter (DAT), which is likely to be hypofunctional, thereby increasing the dopamine concentration and the learning rate. We therefore test the prediction that the SHR learns too fast. Using a variable interval reinforcement schedule, we looked for increased responding within each interval, at around the durations of the last three intervals. At the time predicted by the previous interval, SHR responded significantly (10%) more than their baseline rate, and control WKY rats similarly less than their baseline. At the time predicted by the second (and third) previous intervals, there were minor trends (and no change) in the same direction. In summary, at the times predicted, SHR respond more than control rats. The effect size is insufficient to account for all the differences from control rats, such as their nearly threefold greater operant responding. At the times when SHR increase responding, WKY suppress it. This demonstrates similar learning to the SHR but the opposite response, probably due to anxiety about the bang accompanying reinforcer delivery: WKY are known to have a very negative response to stress. Interval schedules with randomised interval lengths have considerable potential for assessing multiple causes of behaviour, particularly those acting over short timecourses. Alterations in learning rate are not a sufficient explanation for either SHR or ADHD difference from controls.

The Open Orthopaedics Journal, Nov 18, 2011

The contact between a femoral stem prosthesis and the internal surface of the cortical bone with ... more The contact between a femoral stem prosthesis and the internal surface of the cortical bone with the stress in the interface is of crucial importance with respect to loosening. However, there are no reports of strain patterns at this site, and the main aim of the current study was to investigate differences of internal and external cortical strain in the proximal femur after insertion of a stem prosthesis. The external cortical strain of a human cadaveric femur was measured with strain gauges before and after implantation of a stem prosthesis. By use of optical fibres embedded longitudinally in the endosteal cortex, deformations at the implant-internal cortex interface could also be measured. The main external deformation during loading of the intact femur occurred as compression of the medial cortex; both at the proximal and distal levels. The direction of the principal strain on the medial and lateral aspects was close to the longitudinal axis of the bone. After resection of the femoral neck and insertion of a stem prosthesis, the changes in external strain values were greatest medially at the proximal level, where the magnitude of deformation in compression was reduced to about half the values measured on the intact specimen. Otherwise, there were rather small changes in external principal strain. However, by comparing vertical strain in the external and internal cortex of the proximal femur, there were great differences in values and patterns at all positions. The transcortical differences in strain varied from compression on one side to distraction on the other and vice versa in some of the positions with a correlation coefficient of 0.07. Our results show that differences exist between the external and internal cortical strain when loading a stem prosthesis. Hence, strain at the internal cortex does not correspond and can not be deducted from measured strain at the external cortex.

Biophysical Journal, Jul 1, 1999

Using the manipulation force microscope, a novel atomic force microscope, the adhesion forces of ... more Using the manipulation force microscope, a novel atomic force microscope, the adhesion forces of bovine serum albumin, myoglobin, ferritin, and lysozyme proteins to glass and polystyrene substrates were characterized by following the force necessary to displace an adsorbed protein-covered microsphere over several orders of magnitude in time. This force was consistent with a power law with exponent a ϭ 0.37 Ϯ 0.03 on polystyrene, indicating that there is no typical time scale for adhesion on this substrate. On glass, the rate of adhesion depended strongly on protein charge. Forces corresponding to single protein adhesion events were identified. The typical rupture force of a single lysozyme, ferritin, bovine serum albumin, and myoglobin protein adhering to glass was estimated to be 90 Ϯ 10 pN, 115 Ϯ 13 pN, 277 Ϯ 44 pN, and 277 Ϯ 44 pN, respectively, using a model of the experimental system. These forces, as well as the force amplitudes on hydrophobic polystyrene, correlate with protein stiffness.

Langmuir, Sep 19, 1998

ABSTRACT The force acting between a protein molecule and a nonbiological surface is of great impo... more ABSTRACT The force acting between a protein molecule and a nonbiological surface is of great importance in biotechnology. We adsorb protein-covered microspheres on glass and polystyrene substrates in Tris-buffered saline. Using a novel atomic force microscopy technique, we show that proteins adsorb better on hydrophobic than hydrophilic surfaces and that the microspheres adhere with a force characteristic of the particular protein and substrate. The adhesion force on the hydrophobic polystyrene substrate is shown to depend on the structural rigidity of the protein, while on the hydrophilic glass surface, protein and surface charge is more important.

Structural health monitoring (SHM) systems are recognized as a key element in a modern and effici... more Structural health monitoring (SHM) systems are recognized as a key element in a modern and efficient approach to structural lifecycle management. With novel applications of advanced materials, such as extensive use of fibre reinforced composites on aircraft, further advances in monitoring and inspection techniques are required. This is especially relevant for repairs on primary (i.e. load bearing) military aircraft composite structures, where traditional non-destructive inspection methods alone may be insufficient for certification of the repair. Optical fibre sensor systems with continuous in-flight monitoring are considered a promising approach to providing the necessary information on the status of the repaired area. Fibre optic sensor systems commonly involve the use fibre Bragg grating (FBG) sensors bonded to or embedded in the structure. As an element in a certified repair strategy, the limitations of the load transfer from the structure to the sensor must be known. Hence, extensive analysis and testing must be done before introducing any adhesive system/optical fibre combination as part of the SHM system. This paper presents experimental test results obtained for the interface properties of optical fibres with polyimide or Ormocer® coating embedded in an adhesive. Three different adhesives, which are all relevant for military aircraft primary composite structural repairs, are included in the test program. A modified fibre pull-out test setup is applied for estimating the interfacial shear strength (IFSS) for each of the six combinations of adhesive and optical fibre, at two different nominal embedded lengths of 0.5 mm and 1.0 mm. For the polyimide coated fibre, the IFSS values obtained for the three adhesives from fibre pull-out do not differ significantly. The highest IFSS values are obtained at a nominal embedded length of 0.5 mm. The optical fibre with Ormocer® coating seems to have the strongest bond to the adhesives, but results in core pull-out instead of fibre pull-out. The obtained IFSS values for the core/coating interface of the Ormocer® coated fibre are not directly comparable with the IFSS values obtained for the polyimide coated fibre, but they still demonstrate the load transfer properties and the potential of the optical fibre for obtaining accurate strain measurements. As an overall conclusion, the polyimide coated fibre is considered the most appropriate for use in a fibre optic sensor system for SHM.

Proceedings of the International Conference on Port and Ocean Engineering Under Arctic Conditions, 2011

Fiber optic structural monitoring systems are an increasingly popular tool for overload warning, ... more Fiber optic structural monitoring systems are an increasingly popular tool for overload warning, fatigue life management and decision support on ship hull operation. These systems have also found a range of applications outside hull monitoring due to the excellent performance of fiber optic sensor and communication systems in harsh environments. When low noise strain measurements are coupled with structural response models, parameters such as forces, moments, displacements, and structural utilization may be measured on almost any detail of interest. Furthermore, forecasts of extremal observations based on continuous measurements of these parameters are being used to ensure operation within acceptable limits. The authors give an introduction to the measurement and processing techniques and what they offer, and use examples from an Ice Response Monitoring system installed on a Norwegian icebreaker.

Proceedings of SPIE, Jun 12, 2000

ABSTRACT We report on the instrumentation of a high-speed air-cushion catamaran (Surface Effect S... more ABSTRACT We report on the instrumentation of a high-speed air-cushion catamaran (Surface Effect Ship) with more than 50 fibre optic Bragg grating strain gauges, as well as conventional resistive strain gauges, accelerometers, a Motion Reference Unit and Global ...

Proceedings of the National Academy of Sciences of the United States of America, Jan 19, 1999

The adhesion forces of cervical carcinoma cells in tissue culture were measured by using the mani... more The adhesion forces of cervical carcinoma cells in tissue culture were measured by using the manipulation force microscope, a novel atomic force microscope. The forces were studied as a function of time and temperature for cells cultured on hydrophilic and hydrophobic polystyrene substrates with preadsorbed proteins. The cells attached faster and stronger at 37°C than at 23°C and better on hydrophilic than on hydrophobic substrates, even though proteins adsorb much better to the hydrophobic substrates. Because cell adhesion serves to control several stages in the cell cycle, we anticipate that the manipulation force microscope can help clarify some cell-adhesion related issues.

SPIE eBooks, 2000

A fiber Bragg grating sensor system consisting of 56 sensors has been developed to monitor the st... more A fiber Bragg grating sensor system consisting of 56 sensors has been developed to monitor the structural dynamical response of an in-operation composite hull naval vessel. The distributed array of wavelength-division multiplexed Bragg grating strain sensors has been utilized to measure: global hull bending with Bragg grating sensor pairs; local strain concentrations with Bragg grating rosettes; vibrational response of the ship's waterjet propulsion system; and large dynamic strain response in the wet deck region from wave slamming in rough seas. In addition to monitoring the ship's normal vibrations and bending moments, monitoring the response of the ship to wave slamming (i.e. wave impacts) - especially in the wet deck region of the catamaran - is of some importance because it can lead to large scale damage in the ship.

Measurement Science and Technology, Apr 1, 2002

... Sandwich materials may for instance require more sensors than a steel structure due to the po... more ... Sandwich materials may for instance require more sensors than a steel structure due to the potentially ... and consequently the grid of sensors must be fairly dense on a complex sandwich structure such as ... there is a desire to characterize the strain condition in the hull all the way ...

Behavioural Brain Research, Mar 1, 2009

Several existing theoretical models of Attention Deficit Hyperactivity Disorder (ADHD) predict th... more Several existing theoretical models of Attention Deficit Hyperactivity Disorder (ADHD) predict that a high or low learning rate contributes to some cases of ADHD; and that this is controlled by the dopamine signal. The Spontaneously Hypertensive (Hyperactive) Rat has an abnormal Dopamine Transporter (DAT), which is likely to be hypofunctional, thereby increasing the dopamine concentration and the learning rate. We therefore test the prediction that the SHR learns too fast. Using a variable interval reinforcement schedule, we looked for increased responding within each interval, at around the durations of the last three intervals. At the time predicted by the previous interval, SHR responded significantly (10%) more than their baseline rate, and control WKY rats similarly less than their baseline. At the time predicted by the second (and third) previous intervals, there were minor trends (and no change) in the same direction. In summary, at the times predicted, SHR respond more than control rats. The effect size is insufficient to account for all the differences from control rats, such as their nearly threefold greater operant responding. At the times when SHR increase responding, WKY suppress it. This demonstrates similar learning to the SHR but the opposite response, probably due to anxiety about the bang accompanying reinforcer delivery: WKY are known to have a very negative response to stress. Interval schedules with randomised interval lengths have considerable potential for assessing multiple causes of behaviour, particularly those acting over short timecourses. Alterations in learning rate are not a sufficient explanation for either SHR or ADHD difference from controls.

Behavioral and Neural Biology, Sep 1, 1992

Childhood hyperactivity (attention-deficit hyperactivity disorder, ADHD) is a behavior disorder a... more Childhood hyperactivity (attention-deficit hyperactivity disorder, ADHD) is a behavior disorder affecting 2-6% of grade-school children. The main symptoms are attention problems and hyperkinesis. The disorder is commonly treated with psychomotor stimulants, usually methylphenidate hydrochloride (ritalin) or d-amphetamine. Neither the cause of the disorder nor the basis of the effectiveness of the drug treatment is well understood. Differences in reinforcement processes have been implicated as part of the underlying problem. The main purpose of the present research was to investigate reinforcement processes and motor characteristics with and without stimulant medication in SHR, as an animal model of ADHD, and WKY controls, its normoactive progenitor strain. SHR behavior turned out to be more sensitive to immediate reinforcement and proportionately less sensitive to delayed reinforcement when compared to the behavior of WKY, as demonstrated by systematic changes in rates of responding throughout fixed-interval schedules of reinforcement of bar-presses by water. The psychomotor stimulants weakened the control by immediate reinforcers and strengthened the control by delayed reinforcers, with the effect of the drugs being more pronounced in WKY than in SHR. The results are consistent with clinical observations that ADHD children are less willing than others to accept "delayed gratification" and that methylphenidate increases the control of delayed reward over their behavior.

Review of Scientific Instruments, Jun 1, 1999

The manipulation force microscope is a novel atomic force microscope adapted to measuring the for... more The manipulation force microscope is a novel atomic force microscope adapted to measuring the force necessary to displace micron-size samples adhering to surfaces. It has successfully characterized the adhesion of both proteins and living cells to substrates. This instrument enables measurement of samples not previously accessible to atomic force microscopes. Here, we give a detailed account of this new method, and report on computer simulations and models to assist the interpretation of data.

ABSTRACT The authors describe a system which will, at about 10 installations in continuous operat... more ABSTRACT The authors describe a system which will, at about 10 installations in continuous operation after 2002, be the first fiber optic sensor system for ship hull monitoring with a wide user base. The experiences made with these systems in the coming years will provide valuable information on the design, reliability and possible use of such systems, and provide a basis for further development.

Behavioural Brain Research, Mar 1, 2009

Several existing theoretical models of Attention Deficit Hyperactivity Disorder (ADHD) predict th... more Several existing theoretical models of Attention Deficit Hyperactivity Disorder (ADHD) predict that a high or low learning rate contributes to some cases of ADHD; and that this is controlled by the dopamine signal. The Spontaneously Hypertensive (Hyperactive) Rat has an abnormal Dopamine Transporter (DAT), which is likely to be hypofunctional, thereby increasing the dopamine concentration and the learning rate. We therefore test the prediction that the SHR learns too fast. Using a variable interval reinforcement schedule, we looked for increased responding within each interval, at around the durations of the last three intervals. At the time predicted by the previous interval, SHR responded significantly (10%) more than their baseline rate, and control WKY rats similarly less than their baseline. At the time predicted by the second (and third) previous intervals, there were minor trends (and no change) in the same direction. In summary, at the times predicted, SHR respond more than control rats. The effect size is insufficient to account for all the differences from control rats, such as their nearly threefold greater operant responding. At the times when SHR increase responding, WKY suppress it. This demonstrates similar learning to the SHR but the opposite response, probably due to anxiety about the bang accompanying reinforcer delivery: WKY are known to have a very negative response to stress. Interval schedules with randomised interval lengths have considerable potential for assessing multiple causes of behaviour, particularly those acting over short timecourses. Alterations in learning rate are not a sufficient explanation for either SHR or ADHD difference from controls.

The Open Orthopaedics Journal, Nov 18, 2011

The contact between a femoral stem prosthesis and the internal surface of the cortical bone with ... more The contact between a femoral stem prosthesis and the internal surface of the cortical bone with the stress in the interface is of crucial importance with respect to loosening. However, there are no reports of strain patterns at this site, and the main aim of the current study was to investigate differences of internal and external cortical strain in the proximal femur after insertion of a stem prosthesis. The external cortical strain of a human cadaveric femur was measured with strain gauges before and after implantation of a stem prosthesis. By use of optical fibres embedded longitudinally in the endosteal cortex, deformations at the implant-internal cortex interface could also be measured. The main external deformation during loading of the intact femur occurred as compression of the medial cortex; both at the proximal and distal levels. The direction of the principal strain on the medial and lateral aspects was close to the longitudinal axis of the bone. After resection of the femoral neck and insertion of a stem prosthesis, the changes in external strain values were greatest medially at the proximal level, where the magnitude of deformation in compression was reduced to about half the values measured on the intact specimen. Otherwise, there were rather small changes in external principal strain. However, by comparing vertical strain in the external and internal cortex of the proximal femur, there were great differences in values and patterns at all positions. The transcortical differences in strain varied from compression on one side to distraction on the other and vice versa in some of the positions with a correlation coefficient of 0.07. Our results show that differences exist between the external and internal cortical strain when loading a stem prosthesis. Hence, strain at the internal cortex does not correspond and can not be deducted from measured strain at the external cortex.

Biophysical Journal, Jul 1, 1999

Using the manipulation force microscope, a novel atomic force microscope, the adhesion forces of ... more Using the manipulation force microscope, a novel atomic force microscope, the adhesion forces of bovine serum albumin, myoglobin, ferritin, and lysozyme proteins to glass and polystyrene substrates were characterized by following the force necessary to displace an adsorbed protein-covered microsphere over several orders of magnitude in time. This force was consistent with a power law with exponent a ϭ 0.37 Ϯ 0.03 on polystyrene, indicating that there is no typical time scale for adhesion on this substrate. On glass, the rate of adhesion depended strongly on protein charge. Forces corresponding to single protein adhesion events were identified. The typical rupture force of a single lysozyme, ferritin, bovine serum albumin, and myoglobin protein adhering to glass was estimated to be 90 Ϯ 10 pN, 115 Ϯ 13 pN, 277 Ϯ 44 pN, and 277 Ϯ 44 pN, respectively, using a model of the experimental system. These forces, as well as the force amplitudes on hydrophobic polystyrene, correlate with protein stiffness.

Langmuir, Sep 19, 1998

ABSTRACT The force acting between a protein molecule and a nonbiological surface is of great impo... more ABSTRACT The force acting between a protein molecule and a nonbiological surface is of great importance in biotechnology. We adsorb protein-covered microspheres on glass and polystyrene substrates in Tris-buffered saline. Using a novel atomic force microscopy technique, we show that proteins adsorb better on hydrophobic than hydrophilic surfaces and that the microspheres adhere with a force characteristic of the particular protein and substrate. The adhesion force on the hydrophobic polystyrene substrate is shown to depend on the structural rigidity of the protein, while on the hydrophilic glass surface, protein and surface charge is more important.